Onc. Tsiko Marguerite spike issue

[Kelly R]

My little Oncidium Tisiku Marguerite is throwing me for a loop. It came to me a few months ago in spike, but several leaves dropped in shipment. It had about 8 short spikes on it. One has really taken off, but within the week, 2 turned brown, a few weeks later, 2 others turned brown. I am left with 5 - the one that is doing just dandy, 2 had the tips turn bright green like they were going to take off and one of those is turning darker now, and one of the other dormant seeming ones is turning brown. I have no idea what is going on. It has 2 new growths on it that seem to keep growing. One of the front bulbs 3 weeks ago look like it had a little loop growing that was going to be a new spike, but that has shriveled up. The only thing I can think of is the space heater I added to my work area 3 weeks ago. Maybe it is giving off fumes or something that the plant doesn't like.

It gets watered about once a week - with Dyna Pro orchid food (not the bloomer food) at not full strength every other week, and regular water in between. It gets good light right by the window (south east). I will post pictures soon.